The New York Knicks' front office is worried big man Rasheed Wallace, sidelined since mid-December with a lingering left foot injury, will be out for an extended period, possibly the rest of the season, ESPN New York reported, citing two unidentified league sources.

Coach Mike Woodson said as recently as last week that he hoped Wallace, 38, would begin running this week, but he told reporters Wednesday in London that Wallace still has yet to do so.

"He'll be back—but when, I don't know," Woodson said, according to ESPN New York. "We're gradually trying to get him back where he can run again so he can get back in a uniform. But when, we don't know when yet."

Wallace has been out since Dec. 15 with a stress reaction in his left foot, and there are some in the organization who want to pursue a free agent immediately to replace Wallace.

A complicating factor: If the Knicks add a free agent, they would have to cut a player from their active roster and all 15 players’ contracts are guaranteed.

Others in the organization—including Woodson, who coaxed Wallace out of retirement to join the Knicks—want to give him time to heal before making a move to replace him.

The Knicks could use Wallace’s size up front because Marcus Camby is sidelined 2-4 weeks with plantar fasciitis in his left foot, and Amare Stoudemire is still working his way back from offseason knee surgery.

When healthy, Wallace, a 15-year veteran, has been a strong presence in the post, averaging 7.2 points and 3.2 rebounds in 14.6 minutes in 20 games. He also has given the Knicks a strong post defender off the bench.